1. Field of the Invention
This invention pertains generally to configuration ROM implementations for IEEE Standard 1394 nodes. More particularly, the invention is a method and apparatus for presenting a plurality of link devices as separate nodes within a singe serial bus module by generating individual or a distinct configuration ROM image for each link device in the module.
2. The Prior Art
The Institute of Electrical and Electronics Engineers, Inc. (IEEE) defines the IEEE Standard 1394-1995 serial bus architecture in the document xe2x80x9cIEEE Standard for a High Performance Serial Busxe2x80x9d published Aug. 30, 1996 that is incorporated herein by reference. In IEEE 1394, the serial bus architecture is defined in terms of nodes. In general, a node is an addressable entity (i.e., a logical entity with a unique address), which can be independently reset and identified. More than one node may reside on a single module, and more than one unit may reside in a single node.
A module is a physical device, comprising one or more nodes that share a physical interface. The address space provided by a node can be directly mapped to one or more units. A unit is a logical entity, such as a disk controller, which corresponds to unique I/O (input/output) driver software. On a multifunction node, for example, a processor and I/O interfaces could be different units on the same node.
Modules and/or nodes can be xe2x80x9cinterconnectedxe2x80x9d with each other using an appropriate physical topology suitable for use with the serial bus, such as a xe2x80x9cbackplane environmentxe2x80x9d and/or xe2x80x9ccable environmentxe2x80x9d, for example. These environments are described in further detail in Institute of Electrical and Electronics Engineers (IEEE) Standard 1394-1995 xe2x80x9cIEEE Standard for a High Performance Serial Busxe2x80x9d published Aug. 30, 1996. Interconnected nodes may reside in either environment without restriction.
Configuration ROM implementations are well known in the field of serial bus devices and provide the hardware and software specifications of a serial bus node and its associated units. For example in IEEE Standard 1394, two configuration ROM formats are supported: minimal and general. The minimal ROM format provides a 24-bit company identifier. The general ROM format provides additional information in a bus_info_block and a root_directory. Entries within the root_directory may provide information or may provide a pointer to another directory (root-dependent directory and/or unit_directory), which has the same structure as the root_directory. Entries within the root directory may also provide a pointer to a leaf, which contains information. The unit_directories contain information about the units associated with the node, such as their software version number and their location within the address space of the node, for example.
FIG. 1 shows a general ROM implementation format for IEEE Standard 1394. The ROM directory structure is a hierarchy of information blocks, where the blocks higher in the hierarchy point to the blocks beneath them. The location of the initial blocks (inof_length, crc_length, rom_crc_value, bus_info_block, and root_directory) are fixed. The location of the other entries (unit_directories, root and unit leaves) varies according to each vendor, but are specified by entries within the root_directory or its associated directories.
In general, the bus_info_block provides specific information about the node. For example, the bus_info_block may indicate whether the node carries out isochronous data transfers. Additionally, the bus_info_block provides a node_vendor_id field, a chip_id_hi field, and a chip_id_lo field, among other things. Together, the node_vendor_id, chip_id_hi, and chip_id_lo fields form a 64-bit node unique identifier. Other node specific information may be provided in the root_directory and the root leaves of the ROM. Unit specific information is normally provided in the unit_directory and the unit leaves of the ROM. For example, the specification identification and the version number may be provided for a particular protocol in the unit_directory and the unit leaves. IEEE Standard 1394-1995 xe2x80x9cIEEE Standard for a High Performance Serial Busxe2x80x9d published Aug. 30, 1996 describes the general ROM format and its associated blocks in further detail and is incorporated herein by reference.
According to the prior art, a serial bus module may include one or more nodes. For example, FIG. 2 illustrates a typical module device 1 having first and second nodes 2a, 2b. Nodes 2a, 2b include respective link layer services (LINK) 3a, 3b and physical layer services (PHY) 4a, 4b. Each link device 3a, 3b includes a respective global unique identifier (GUID) 5a, 5b to identify each node device 2a, 2b. 
Presently, the configuration ROM described above is managed by software operating at the transaction layer 6 in module 1. However, current transaction layer implementations which support multiple link devices (such as depicted in FIG. 2) present a single configuration ROM image 7 for both link devices. As a result, transaction layer software 6 presents nodes 2a and 2b as the same GUID, which may result in inconsistent information provided to the serial bus 8.
Other node or module devices (not shown) attached to serial bus 8 may query module 1 to ascertain certain configuration data associated with module 1. For example, a remote node may query module 1 to ascertain, among other things, the node configuration of module 1 and/or the units presented by the nodes of module 1. These remote nodes query module 1 using one of various request commands. Some remote nodes request information xe2x80x9cby quadletxe2x80x9d and other nodes request information xe2x80x9cby blockxe2x80x9d, for example.
When a request is made by quadlet, the corresponding link devices 3a, 3b provide the requested data from the hardware registers 9a, 9b associated with the respective link device 3a, 3b. In this manner, link device 3a provides the requested data from its hardware registers 9a, and link device 3b provides the requested data from its hardware registers 9b. 
However, when a request is made by block, the requested data is provided from the configuration ROM 7 which is normally managed by the transaction layer software 6. As noted above, present transaction layer implementations provide a single configuration ROM 7 for multiple link devices 3a, 3b. Thus the data provided in conjunction with a request by block may be different and inconsistent with that provided had the request been made by quadlet.
Accordingly, there is a need for a method for presenting a plurality of link devices as separate nodes within a single serial bus module by generating an individual or distinct configuration ROM image for each link device in the module so that when a request is made to the module, accurate and consistent data is provided to the requesting device. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the background art.
An object of the invention is to provide a method for supporting multiple link devices in a single module that overcomes the deficiencies of the prior art.
Another object of the invention is to provide a method for presenting a plurality of link devices as separate nodes within a single serial bus by providing an individual configuration ROM for each link device in the module.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing the preferred embodiment of the invention without placing limitations thereon.
The present invention is a method and apparatus embodied in transaction layer software suitable for use with serial bus devices, such as IEEE standard 1394 serial bus devices. The invention further relates to machine readable media on which are stored embodiments of the present invention. It is contemplated that any media suitable for retrieving instructions is within the scope of the present invention. By way of example, such media may take the form of magnetic, optical, or semiconductor media. The invention also relates to data structures that contain embodiments of the present invention, and to the transmission of data structures containing embodiments of the present invention.
In its most general terms, the invention comprises software for supporting multiple link devices in the same physical module as separate nodes by presenting individual or distinct configuration ROMs for each link device to the serial bus. In the preferred embodiment, the software comprises IEEE standard 1394 transaction layer software (TNF kernel) for a serial bus module attachable to an IEEE standard 1394 bus. The software is executed by a conventional processor within the module device as is known in the art.
The serial bus module may include one or more link devices operatively coupled for communication with the TNF kernel. In other exemplary embodiments, device driver services may be used to manage communication between the TNF kernel and the link devices as is known in the art.
The TNF kernel carries out the operation of ascertaining or becoming aware of the link devices in the modules, creating an individual configuration ROM for each link device, and presenting the created configuration ROMs to the other devices on the 1394 bus to thereby present each link device in the module as a separate node.
The TNF kernel ascertains each link device normally during initialization of the module, either through a predefined startup routine or through notification from device driver services, if such services are implemented in the module. The TNF kernel ascertains, among other things, each link device""s GUD (globally unique identifier).
For each link device, the TNF kernel creates a data structure suitable for storing data associated with each link device. In an exemplary embodiment of the invention, the TNF kernel uses a data structure comprising a list of link data records, one record for each link device. Each link data record includes a CSR (control and status register) address map and Configuration ROM image storage and/or support thereof. Each Configuration ROM image is constructed using, among other things, the information for each link device and includes an entry for the link device GUID. The CSR address map is a data structure that, among other things, points to the active configuration ROM. In one of a number of possible embodiments, the present invention may employ dynamic configuration ROM using double image buffers which is described in copending application ser. No. 09/1431,703 having the title xe2x80x9cA SYSTEM AND METHOD FOR PROVIDING DYNAMIC CONFIGURATION ROM USING DOUBLE IMAGE BUFFERSxe2x80x9d filed on Nov. 1, 1999 and is incorporated herein by reference.
Requests by other devices to the module are communicated from the serial bus to the physical layer device in the present module. Communications for layers higher than the physical layer are then communicated to the link layer device for further processing.
When a request by quadlet is made to the module, the appropriate link device provides the appropriate information from the link device""s registers as is conventionally carried out.
However, when a request by block is made to the module, the request is communicated from the corresponding link device to the TNF kernel. In addition, the link device provides its unique software ID (Link ID) along with the request. In response to the block request, the TNF kernel provides the configuration ROM for the appropriate link device according to the Link ID. Since individual configuration ROMs are created for each link device in the module, the information provided by the TNF kernel via the individual configuration ROM is consistent with information provided in response to requests made by quadlet as described above.